Cantilever Force Distribution on Jack-Up Rig

Abstract

Cantilever is the most important structure of the jack-up rig. Jack-up usually has three working conditions: drilling condition, storm condition, preloading condition. The fulcrums of the cantilever in the drilling condition are less than the other two. So the distribution of the cantilever force in the storm and preloading conditions becomes extremely complicated with the increase of fulcrums. In order to facilitate the evaluation of jack-up rig strength, a simplified analytical method and a finite element method (FEM) are presented to distribute the cantilever force on a jack-up rig during the storm and preloading conditions. For the simplified analytical method, the fulcrum force is obtained from the distance between the fulcrum and the position of the cantilever resultant force. For the FEM, the cantilever is assumed to be perfect rigid body without any strain. The fulcrum force is calculated according to the balance of the fulcrum forces. Both results of fulcrum force are analyzed and compared. It is shown that they are in good agreement. Thus both methods can be applied in distributing the cantilever force to evaluate the strength of jack-up rig.